This invention relates broadly to a method for producing a multi-shot, plastic injection molded component consisting of at least two independent elements which are rotatable but not detachable relative to each other, and can allow or restrict the passage of fluid therethrough.
In the control of fluid flow, that is liquid and gases, there are a multitude of valve structures which are constructed of various plastic materials. Multiple plastic components are variously connected together in order to provide relative movement of one part relative to at least one other part. Some relative valve movement is of the sliding variety, while other valve movement is based on rotation. Previously, such parts were manufactured individually and assembled in various manual or automatic processes. With the development of multi-shot, injection molding, it has become possible to produce a valve having at least two parts to be connected non-detachably but rotatably relative to each other by molding such parts together in a manner which will allow selective alignment of one part relative to the other.
One known method for injecting molding objects of at least two parts such as used in the utensil application, is disclosed in U.S. Pat. No. 5,298,215 issued Mar. 29, 1994. In this patent, a first part is molded to form an approximately hollow, cylindrical element defining a mold recess. A subsequently produced second part is injection molded partially into the mold recess of the first part so as to outwardly or inwardly deform the hollow, cylindrical element with an undercut in a rotationally symmetric manner by means of pressure from material injected into the mold recess. That is, the plastic is continuously distorted to form the undercut.
Notwithstanding the attempts of the prior art, it remains desirable to provide an improved method for producing a plastic, multi-shot, injection molded valve, wherein at least two non-detachable, rotatably connected parts are formed with cooperating passageways which will selectively permit the flow of fluid therethrough. It is also desirable that such method requires no means of distorting either of the parts.
It is one object of the present invention to provide a method of multi-shot, plastic injection molding to form a valve.
It is an additional object of the present invention to provide a method of injection molding a valve, wherein a first shot is used to produce a housing, a second shot is used to produce a rotatable pit cock, and a third shot is used to produce an adapter grommet for coupling the valve to an adjacent valve or related equipment.
It is another object of the present invention to provide a valve in which it is no longer necessary to manufacture the valve components separately, and then assemble the separate components.
It is also an object of the present invention to provide a method of manufacturing a valve using various types of plastic.
It is a further object of the present invention to provide an economical valve manufacturing process, such that the valve components do not enter into a bonding connection so that the rotational mobility of the components is ensured.
Another object of the present invention is to provide a unitized injection molding assembly which relies on a cooperating rib-undercut structure.
In one aspect of the invention, there is provided a method for the multi-shot injection molding of at least two independent parts such that at least two of the parts are rotatable relative to each other and are not detachable from each other so as to form a valve. The valve in one state has one part rotated relative to the other part, such that both liquid and gas pass through both parts. The valve in a second state has the one part rotated relative to the other part, such that both liquid and gas do not pass through one of the two parts. The method includes the step of injection molding one of the two parts in the form of a cylindrical tube which has a first passage running through the part perpendicular to the cylindrical tube. The one part also has a substantially cylindrically-shaped retaining rib inside the cylindrical tube. The method also includes the step of injection molding the other part in the form of a cylinder inside the cylindrical tube of the one part without distorting either of the parts, so as to have plastic molded around all exposed edges of the rib of the one part, so as to rotatably retain the other part inside the one part. The other part also has a second passage running therethrough. The second passage is selectively aligned with the first passage on the one part upon rotation of the other part. The method further includes injection molding a substantially cylindrical adapter grommet adapted to couple the two parts to related valve equipment. The one part is embodied in a stationary housing and the other part is embodied in a rotatable pitcock. The pitcock is formed with an undercut which will receive the rib.
In another aspect of the invention, there is provided a multi-shot, injection molded valve having at least two independent elements which are rotatably and non-detachably connected together. The valve includes a stationary housing and a pitcock rotatably mounted therein. The stationary housing is molded in a first shot with at least one inlet projecting from one side of the housing and at least one outlet projecting from another side of the housing, the inlet and outlet defining a first passageway. The housing has a substantially cylindrical upper portion defining a first bearing surface, and a substantially cylindrical portion defining a second bearing surface, the upper and lower portions being divided by substantially cylindrical rib. The pitcock is molded in a second shot with an external grip portion, an upper cylindrical segment beneath the grip portion and a lower cylindrical segment separated from the upper cylindrical segment by a substantially cylindrical undercut which is engageable with the rib on the housing. The pitcock is also provided with a second passageway which is selectively aligned with the first passageway of the housing upon rotation of the pitcock in the housing. The inlet has a generally tubular formation with a reduced adapter portion, and the outlet has a generally tubular formation having a barbed construction. A generally tubular adapter grommet is engageable with the inlet and/or outlet, and is injection molded in a third shot. The housing includes a planar grip portion extending outwardly therefrom. The upper cylindrical segment is engageable with the first bearing surface, and the lower cylindrical segment is engageable with the second bearing surface.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.